Bug 2360211 (CVE-2025-23138)

Summary: CVE-2025-23138 kernel: watch_queue: fix pipe accounting mismatch
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
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Hardware: All   
OS: Linux   
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Description OSIDB Bzimport 2025-04-16 15:02:51 UTC 
In the Linux kernel, the following vulnerability has been resolved:

watch_queue: fix pipe accounting mismatch

Currently, watch_queue_set_size() modifies the pipe buffers charged to
user->pipe_bufs without updating the pipe->nr_accounted on the pipe
itself, due to the if (!pipe_has_watch_queue()) test in
pipe_resize_ring(). This means that when the pipe is ultimately freed,
we decrement user->pipe_bufs by something other than what than we had
charged to it, potentially leading to an underflow. This in turn can
cause subsequent too_many_pipe_buffers_soft() tests to fail with -EPERM.

To remedy this, explicitly account for the pipe usage in
watch_queue_set_size() to match the number set via account_pipe_buffers()

(It's unclear why watch_queue_set_size() does not update nr_accounted;
it may be due to intentional overprovisioning in watch_queue_set_size()?)
Comment 1 Avinash Hanwate 2025-04-17 14:29:47 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025041634-CVE-2025-23138-a5c8@gregkh/T